1. Field of the Invention
The present invention relates to an apparatus for dubbing a magnetic tape such as video soft tape, audio soft tape or computer soft tape, etc., at high speed and a device for producing a divided master tape for high speed dubbing.
In this specification, terms involving a tape speed are defined in accordance with the following definitions:
"N Speed Playback"
To playback a tape at a running speed which is N times the speed with which the tape is recorded, where N is an integer larger than 1.
"N Speed Recording"
To record a signal reproduced from a master tape played back according to the "N speed Playback" on a recording medium, or to record a signal on a tape running at a speed which is N times a nominal playback speed of that tape, where N is an integer larger than 1.
"N Speed Dubbing"
A dubbing operation in which a master tape for dubbing is played back according to the "N speed Playback" and a resultant reproduced signal thus obtained is recorded as a recording signal on a slave tape running at a speed which is N times a nominal playback speed of the slave tape, where N is an integer larger than 1.
In this case, although a transfer rate of the recording signal from a master tape playback device to a slave tape recording device is N times that of the original recording signal which is used for recording the master tape, actual running speeds of the master and slave tapes are not necessarily identical each other but they can be different each other in this "N Speed Dubbing" operation.
"Double Rate"
A status of signal transfer rate which is twice an original transfer rate (signal transfer rate used for master tape recording).
"Triple Rate"
A status of signal transfer rate which is three times an original transfer rate (signal transfer rate used for master tape recording).
"Triple rate" when referred to in a dubbing apparatus, is also referred to as "triple speed".
"Real Time Speed"
This represents the "N Speed Playback", the "N Speed Recording", or the "N Speed Dubbing" where N is 1, or a tape speed which is equal to its original or nominal speed. "Real time speed" is also referred to as "standard speed" or "normal playback speed", at which the recoded video and/or audio signal is played back to produce normal picture and/or sound for users.
"Double Speed"
This represents the "N Speed Playback", the "N Speed Recording", or the "N Speed Dubbing" where N is 2.
2. Description of the Related Art
A dubbing apparatus in which a signal reproduced by a master tape playback device is supplied to a plurality of slave recording devices to dub the signal on slave magnetic tapes in real time has been known.
Further, a contact print method in which a mirror image tape signal pattern is provided on a master tape having relatively large coercive force and is transferred to a slave magnetic tape by making a magnetic surface of the master tape in intimate contact with the slave magnetic tape while externally applying a low frequency magnetic field thereto has been known as a high speed dubbing system.
Since the former conventional dubbing system is of a real time dubbing system in which the slave tapes are running at their nominal playback speed and recorded with a signal obtained by playing back the master tape at its recording speed, efficiency of slave tape production is low. As to the contact print method, there are problems of degradation of signal frequency characteristics and/or S/N ratio.
Besides, in a digital VTR, etc., according to D2 standard (one of the Industry standards for digital video tape recording), an accompanying audio signal becomes discontinuous at a tape editing point. In order to prevent such signal discontinuity from being reproduced as noise, such audio signal is faded in at an editing start point and faded out at an editing end point, with a silence period of about 3 msec therebetween.
Therefore, when a divided master tape is produced or a produced divided master tape is played back by using such VTR, an audio signal becomes discontinuous at an editing point provided during production of the divided master tape.